Real Time Forecasting Technology For Whole Ship Attitude

Large ships equipped with radar,photoelectric sensor,aircraft and other weapons system,the equipment needs the high precise accuracy information which is obtained by the present dada.Traditional methods relay on the local reference of each device to provide attitude information.However,with the increase of the shipboard equipment of attitude accuracy is improved,the traditional method is difficult to meet the application requirements.In this paper,the research on the short term prediction of ship's attitude and the prediction of angular deformation is carried out,therefore,according to the attitude of limited number of points to predict the attitude of random point on the ship.The main jobs of this thesis are presented as follows(1)Two hybrid EMD-AR model and hybrid WD-AR model were established.First,describing the traditional time series algorithms of short-term prediction of ship motion based on AR model.Second,introduce Empirical mode decomposition(EMD)and wavelet decomposition technique into AR model for their good ability in processing nonlinear and non-stationary signals.The hybrid forecasting model is more accurate than the traditional forecasting model.For WD-AR model,the relative error of the pitch prediction is reduced by an average of 4.4% to 6.92%.The relative error of the roll prediction is reduced by an average of 2.93% to 7.61%.For EMD-AR model,the relative error of the pitch prediction is reduced by an average of 2.9% to 8.43%.The relative error of the roll prediction is reduced by an average of 1.83% to 8.71%(2)Combined with the characteristics of different methods,the hybrid EMD-WD-AR model was established.Compared with traditional AR model,the EMD-WD-AR model has a good predict performance.The relative error of prediction for pitch has reduced by 4.8% and the up to 6.5%,accordingly,the relative error of prediction for roll has reduced by 4.8% and up to 7.05%.(3)A semi-empirical prediction model was established.According to two-dimensional Hydro-elasticity theory and mode analysis theory,physical equations of deck flexure caused by excitation forces imposed on the structure of hull are resented.The minimum relative error of dynamic flexure was 8.7%.The minimum relative error of dynamic flexure was 13.68%.(4)A hybrid prediction model in time domain and spatial domain was established.The model not only can provide real time accurate flexure information for random position on ship,but also can provide the flexure information ahead of time in 5s on this point.The minimum relative error of dynamic flexure in 5seconds ahead of time can reach 15%.